To assess if the MDR and Zn tolerance chir99021 of the isolate Zn3E13 could be transferred by horizontal gene transfer, this isolate was conjugated with the recipient strain E. coli J53. Transconjugants acquired resistance to amoxicillin (AML), ticarcillin (TIC), cephalotin (CP), ceftazidime (CEF), meropenem (MER), sulfamethoxazole (SUL), sulfamethoxazole/trimethoprim (SXT), streptomycin (STR), and tetracycline (TET) and the plasmid replicon types FIB, HI2, Y, A/C and Frep. However, metal tolerance was not transferred since, the MIC values for Cd, Cu and Zn of the respective transconjugant were identical to that of the recipient strain, of 0.1, 0.1 and 1 mM, respectively. While the MIC of the donor strain (Zn3E13) were of 1, 0.5 and 10 mM, respectively. Transfer of the copA gene could not be assessed since the E. coli J53 harboured this gene ( Yi et al., 2012).
3.2. Isolates recovered from Cu- or Zn-enrichment cultures
Identification and phenotypic characterisation [minimal inhibitory concentration of metal (MIC) and antibiotic resistance profiles (black: resistant; grey: sensitive or intermediate)] of isolates recovered from two hospital wastewater cultures (1, 2) enriched with either, Cu or Zn.AML, amoxicillin; TIC, ticarcillin; CP cephalothin; CEF, ceftazidime; MER, meropenem; CT, colistin sulphate; SUL, sulfamethoxazole; SXT, sulfamethoxazole/trimethoprim; TET, tetracycline; GEN, gentamicin; STR, streptomycin. None of the isolates evidenced resistance to ciprofloxacin.* Gene copA-like detected in these strains.Full-size table